Fiber opening technology is expected to improve mechanical characteristics of woven fabric composites by high impregnation of matrix resin and reduction of undulation of yarns. In this paper, a three-dimensional finite element method based on damage mechanics has been applied to plain woven fabric composites, and the effect of fabric architecture of opened yarns on damage development under on-axis tensile load have been investigated numerically. Finite element models composed of weave yarns and matrix were employed, the flattening ratio between width and height of opened yarns were changed under the condition that volume fraction of fiber is constant. As a result, it has been recognized that plain woven fabric composites show different damage development in a mesoscopic scale according to geometric change of opened yarns. Overall tensile strength proved to be maximized by geometric design of opened yarns.

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Precise fineness measurement for a high stiffness staple fiber is difficult by a conventional vibration type fineness meter because the conventional fineness meters are based on the vibration of a string, i.e., a long body without stiffness. Thus, we have developed a new electrostatic vibration type full-digital fineness meter based on the theory of bending vibration. The fineness meter was also designed to automatically measure the fineness at an optimal condition for each sample fiber and to effectively reduce the data noise by a numerical method. We measured the fineness of several fibers by the new fineness meter. The new fineness meter was confirmed to give a quite accurate value of fineness compared to the conventional type fineness meters.

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